1. Field of the Invention
The present invention generally relates to iontophoretic drug delivery devices, and more particularly relates to electronic circuits for use in iontophoretic drug delivery devices which deliver a controlled voltage or current to a patient receiving medication transdermally.
2. Description of the Prior Art
Iontophoresis may be defined as the electrically driven application of drugs or medications, in their ionic form, to the surface tissues of a patient. The application of electric current causes the migration of ions into the tissue, where such migration is proportional to the quantity of current applied through the iontophoretic system.
A basis iontophoretic device includes a controller and a drug delivery device, commonly called a transdermal patch. The controller may include a power source and a circuit to control the application of voltage or current from the power source to the patch. The patch generally includes two or more electrodes, the ionic medication and an electrolyte. When the patch is placed against the skin of the patient and a voltage is impressed across the electrodes, a circuit through the patient's skin is created and current flows through the skin of the patient, driving the ionic medication into the skin and tissue to be absorbed by the patient's body.
In some applications, it may be desirable to increase the voltage provided to the patch electrodes from the power source. This is especially true when the iontophoretic device is battery powered, and it may be necessary to increase a relatively low battery voltage to a higher, but safe, electrode voltage to more effectively drive the ionic medication into the skin and tissue of the patient. In such applications, a boost circuit or step-up DC--DC converter may be suitable for use, such as shown in FIG. 4 of U.S. Pat. No. 5,306,235.